THE INFLUENCE OF CHEMICAL FACTORS 



79 



Eledone moschata and the fishes Con's and Sargus annularis] the 

 oxygen consumption is within wide limits practically independent of 

 the oxygen tension of the water. With very low oxygen pressures 

 symptoms of asphyxiation were observed. It must be assumed that 

 normally the tissues of these animals contain free oxygen. 



TABLE VII. EXAMPLE CARCIKUS M CRN AS. 



In hyaline pelagic animals with a very small proportion of dry sub- 

 stance (Pelagia, Carmarina, with less than I per cent, of dry substance, 

 according to Vernon [1876]) (see below, p. 144) the oxygen con- 

 sumption is also independent of the oxygen pressure, and it is rea- 

 sonable to assume that a positive pressure of oxygen is found in all 

 the tissues. Finally, in forms which have a comparatively high 

 proportion of dry substance and very imperfect respiratory and 

 circulatory arrangements, the oxygen consumption is clearly dependent 

 on the oxygen pressure of the water, and approaches a maximum, 

 which is attained only when the oxygen pressure is higher than the 

 normal. 



TABLE VIII. EXAMPLE A NEMONIA SULCATA. 



In this latter case Henze assumes that the oxygen pressure in 

 the tissues or in some of them at least is normally o, but that a posi- 

 tive pressure may be produced when there is a sufficiently high oxygen 

 pressure in the water. It was directly observed on Sipunculus that 



1 Henze's figures are in arbitrary units. The oxygen quantity, 28-5, corresponds to water 

 saturated with atmospheric air. 



